diff --git a/classes/AdminController.php b/classes/AdminController.php
index 3f8c770ee..060dc9a63 100644
--- a/classes/AdminController.php
+++ b/classes/AdminController.php
@@ -1684,7 +1684,7 @@ class AdminControllerCore extends Controller
 		/* Checking for fields validity */
 		foreach ($rules['validate'] as $field => $function)
 			if (($value = Tools::getValue($field)) !== false && ($field != 'passwd'))
-				if (!Validate::$function($value))
+				if (!Validate::$function($value) && !empty($value))
 					$this->_errors[] = $this->l('the field').
 						' <b>'.call_user_func(array($class_name, 'displayFieldName'), $field, $class_name).'</b> '.
 						$this->l('is invalid');
diff --git a/classes/ObjectModel.php b/classes/ObjectModel.php
index 8ed4d85df..1e26508ad 100644
--- a/classes/ObjectModel.php
+++ b/classes/ObjectModel.php
@@ -564,7 +564,7 @@ abstract class ObjectModelCore
 			// Hack for postcode required for country which does not have postcodes
 			if ($value = Tools::getValue($field, $this->{$field}) OR ($field == 'postcode' AND $value == '0'))
 			{
-				if (!Validate::$function($value))
+				if (!Validate::$function($value) && (!empty($value) || in_array($field, $this->fieldsRequired)))
 					$errors[] = '<b>'.self::displayFieldName($field, get_class($this), $htmlentities).'</b> '.Tools::displayError('is invalid.');
 				else
 				{